The present invention relates to a novel device for trimming grains and seeds, so-called "aristate" grains and seeds because their caryopsises extend in an awn, such as the grain or seed of the grass of the genus bromus (bromus catharticus). It is said that such grains or seeds are difficult to sow by means of a machine as their awns intermingle and prevent them from flowing steadily into the channels of the device. The result is an irregular seed-bed. In some areas there is little or no seed whereas in other places there is too much seed. Consequently the use of seed per hectare is out of proportion. The efficiency could be doubled.
In order to remedy the abnormal use of seed it has been suggested to trim the seeds beforehand, either by hurling them vigorously against a rough surface or by threshing them with a flail (such as in German Pat. No. 322512). Such methods are not acceptable for certain species which are too fragile to stand up to such a treatment without being damaged.
The obvious thought is to cut or to singe the awns but in order to prevent the seeds from being damaged during the operation it is not only necessary to keep them upright so as to cut them correctly but also to protect them against destruction of the awns during the operation.
German Pat. No. 915873 therefore suggests to singe the awns and the husks of the seeds by throwing them in the flame of a burner. This method has the disadvantage that the awn and the husk may be destroyed at once as the heat may burn the caryopsis not only superficially but often to the extent that it reaches the core thereby sterilizing the germ.
The problem to overcome is therefore to maintain the grain in a predetermined position during the trimming operation. The problem is even greater if one considers that, on the one hand, for the sake of efficiency a multitude of seeds has to be treated simultaneously, whereas on the other hand, the dimensions of each seed are very small. In effect, the problem consists of two parts, namely to provide a steadfast orientation to the grain and to maintain it in this orientation during the trimming operation.
It has already been suggested to orient the grains of the kind described above by placing them in a strong current of air so as to move them toward a screen whereby the awns act as arrows. In French Pat. No. 1,244,464 filed by Monsieur Roger LOISEAU on Sept. 18, 1959, this orientation method is used to sort grains having an eccentric caryopsis such as Ray-grass. The inventor has tried to use an analogous method to solve the problem described above but it was soon noted that no results could be expected because, although the grains carried away by the air current assumed a unique orientation, the second part of the problem could not be solved. In other words, the principle is perfectly sound for a dynamic process but not for a continuous one.
U.S. Pat. No. 2,750,977 discloses a device for peeling onions having a conveyor comprising a sturdy metallic mesh which causes the onions to pass in front of a knife blade while the onions are maintained in a substantially vertical position by means of a flow of air passing through the conveyor. Although this specification suggests orienting the product to be treated by means of air under high pressure, it is impracticable to follow this suggestion for the material in question. An onion has sufficient weight to put it into a vertical position by means of gravity but a grain is light and does not allow using high pressure. Its shape does not allow a stable position especially in such a device and it would be difficult to feed the product, i.e. the grains, already oriented to the conveyor.